nix: don't send tarballTtl to the daemon

it's an eval-time only setting, the daemon doesn't use it anywhere. this
is a hack, but until we have a much better settings system we are stuck.

fixes #680

Change-Id: I532088b0279f13da0a0a65c2bd2e5f9d1dfb39da
(cherry picked from commit 5917db84aa)

lix/libstore/remote-store.cc

@@ -147,6 +147,7 @@ void RemoteStore::setOptions(Connection & conn)
     overrides.erase(experimentalFeatureSettings.experimentalFeatures.name);
     overrides.erase(settings.pluginFiles.name);
     overrides.erase(settings.storeUri.name); // the daemon *is* the store
+    overrides.erase(settings.tarballTtl.name); // eval-time only, implictly set by flake cli
     conn.to << overrides.size();
     for (auto & i : overrides)
         conn.to << i.first << i.second.value;